Airworthiness Design Research Articles

A Systematic Approach towards the Integration of Initial Airworthiness Regulatory Requirements in Remotely Piloted Aircraft System Conceptual Design Methodologies

The regulatory framework of Remotely Piloted Aircraft Systems (RPASs) has recently experienced an extraordinary evolution. This article seeks to improve the integration of certification considerations in RPAS conceptual design approaches so as to enhance the safety, certifiability and competitiveness of their resulting designs. The first part of the research conducts a two-stage analysis of contemporary regulations related to an RPAS’s initial airworthiness. In the first stage, the broad international regulation paradigm is evaluated attending to a set of criteria that are tightly related to both airworthiness and design considerations. The second stage keeps the most promising documents from a design–integration standpoint, which are assessed according to their applicability considering both design and operational aspects. The results of this analysis provide insights regarding the main issues in airworthiness design criteria extraction and integration in design methodologies. To aid the designer in surmounting these challenges, a flexible procedure named DECEX is developed. Considering the documents and findings from the survey, and attending to the scope of the design methodology being developed, it aids in establishing a complete regulatory document corpus and in comparing and extracting the applicable airworthiness design criteria. Two case studies for different RPAS types are conducted to demonstrate its application.

Research on pressure dynamic characteristics of multi-cavity model in aero-engine secondary air system

An algorithm for the basic elements was established based on the physical mechanism of transient secondary air system. A simulation program was compiled by using object-oriented language. Then a multi-cavity transient model of the secondary air system was established, and the pressure dynamic characteristics of the multi-cavity model were analyzed. The transient modeling of the air system has practical engineering versatility by establishing a standard interactive interface, and the transient modeling and analysis of the air system in different engines can be realized through using each component module. Such simulation research can help engineers to improve the design flow path of the secondary air system, and provide simulation data for the airworthiness design of engine, which has certain application value.

Efficient Numerical Integration Algorithm of Probabilistic Risk Assessment for Aero-Engine Rotors Considering In-Service Inspection Uncertainties

Numerical integration methods have the characteristics of high efficiency and precision, making them attractive for aero-engine probabilistic risk assessment and design optimization of an inspection plan. One factor that makes the numerical integration method a suitable approach to in-service inspection uncertainties is the explicit derivation of the integration formula and integration domains. This explicit derivation ensures accurate characterization of a multivariable system’s failure risk evolution mechanism. This study develops an efficient numerical integration algorithm for probabilistic risk assessment considering in-service inspection uncertainties. The principle of probability conservation is applied to the transformation of the integration domain from the current flight cycle to the initial (N = 0) computational space. Consequently, the integration formula of failure probability is deduced, and a detailed mathematical demonstration of the proposed method is provided. An actual compressor disk is evaluated using the efficient numerical integration algorithm and the Monte Carlo simulation to validate the accuracy and efficiency of the proposed method. Results show that the time cost of the proposed algorithm is dozens of times lower than that of the Monte Carlo simulation, with a maximum relative error of 5%. Thus, the efficient numerical integration algorithm can be applied to failure analysis in the airworthiness design of commercial aero-engine components.

A discussion of airworthiness in terms of safety and integrity

System safety and integrity are regarded as two main aspects in aircraft airworthiness. Both are widely used in airworthiness design, verifying, and certifying. Firstly, a depth of understanding about the concept of airworthiness is given, and the total process of airworthiness based on safety standards and integrity ones is proposed. Secondly, airworthiness’ main aspects are discussed with the traditional safety assessment, current standards, STAMP and STPA. Lastly, the relationship between reliability, maintenance, safety, integrity and airworthiness is analysed.

Flammable Fluid Fire Protection Airworthiness Design and Verification Method of Civil Transport Aircraft

Nowadays, civil transport aircraft designers attach importance to designated fire zone and always ignore the flammable fluid leakage zones, which may threaten the safety of aircraft. The main content of the research are as follows: Firstly, this paper starts from the civil transport category aircraft flammable fluid related airworthiness requirement (§25.863), including the research of development background, related advisory circular and main general compliance verification method. The compliance verification process of §25.863 is given. General protection measures include drainage and ventilation, separation and isolation of leakage from ignition sources, component qualification, cooling air ducts, condition monitoring, detection and accommodation, and fire protection. Secondly, design considerations and compliance verification methods of the systems of the civil transport aircraft are given. Finally, in view of the characteristic of the typical civil transport aircraft configuration, zonal safety analysis method is adopted to research the source of ignition control requirement and method, the ventilation and draining design requirement and method. The research product is used for the fire protection design and the compliance certification of the airworthiness requirement of civil transport aircraft flammable fluid leakage zone.

The Study of Transport Category Aircraft Fire Safety Airworthiness Design

This paper discussed the classification of aircraft zones related to fire based on the existence and characteristics of aircraft flammable fluids and ignition sources as well as fire safety provisions in order to establish the aircraft level safety requirements. Then, the aircraft fire safety airworthiness design process has been presented to allocate the aircraft level safety requirements in terms of zones. And the aircraft manufacturers can use this process as a guidance to perform their fire safety design and demonstrate the compliance of aircraft fire safety.

Safety and Airworthiness Design of Ultra-Light and Very Light Amphibious Aircrafts

Ultra-light and very light amphibious aircrafts are the special kinds of low-speed general aircrafts. They are low weighted and small sized but can takeoff and land either on land or water without changing the structure of any parts. These characteristics result in the distinctive configuration and structure design, and meanwhile bring about significant features of safety and airworthiness design. These problems are investigated by developing the ultra-light amphibious aircraft “Frigate bird” and analyzing the other aircrafts’ design. This paper mainly discusses the preliminary design about structure, aerodynamics, power effect, flying qualities, dynamics and statics on water. Some analysis methodologies and design parameters which are different from the conventional general aircrafts’ are also represented.

A Method to Calculate the Aircraft Ground Minimum Control Speed Based on Mathematical Simulation

The airworthiness compliance of the ground minimum control speed (VMCG) must be shown before the type certificate of a transport category airplane is issued under CCAR-25. A method to calculate VMCG based on mathematical simulation is provided. All forces and moments act on the aircraft in the takeoff run are considered in this method. The model of the pilot's operation in airworthiness compliance flight test of VMCG is established in this method, and the time interval between the instant at which the critical engine is failed and the instant at which the pilot recognizes and reacts to the engine failure is considered in the model. Based on this method, VMCG is obtained through the mathematical simulation of the takeoff run of an aircraft after the critical engine is failed. VMCG calculated by the method presented in this paper can be used to guide the airworthiness design and VMCG flight tests of an aircraft.

Application of Parameter Estimation to Improved Autogyro Simulation Model Fidelity

Development of an airworthiness design standard for light autogyros is underway in an attempt to improve a poor safety record. Mathematical modeling is playing a vital role in the understanding the flight mechanics of these rotorcraft. Unlike helicopters, autogyros have not received the attention of the technical community until recently, and, as a consequence, there is little theoretical analysis or experimental flight testing that makes use of contemporary methods. As a result, validity of mathematical modeling has relied on analysis of flight-test data from experiments conducted with two different aircraft. Parameter estimation by the use of a simple frequency-domain, equation-error approach has proved to yield consistent and robust results from each aircraft, highlighting the same mismatches between theory and experiment in both cases

Impact of safety requirements on the weight of civil unmanned aerial vehicles

The lack of airworthiness and certification criteria for the employment of UAV vehicles in the civilian field has caused an uncontrolled proliferation of projects and the construction of a number of UAV prototypes which differ in dimension, weight, flight characteristics and payload carriage. This paper is aimed at identifying the most important project criteria which may concur to unifying the main UAV characteristics. In particular, the minimum take‐off weight is investigated which is able to guarantee the adherence to the levels of safety required by the airworthiness design requirement (ADR) currently being developed. To this end, the characteristics of mission and the safety requirements currently available in the ADR have been examined. and the safety characteristics and reliability of the UAVs used in the military field have also been considered. After which, an assessment is made of the on‐board system and the relative redundancies necessary for adjusting such characteristics to meet the ADR. Taking into account the weight of systems, payload and other UAV components (engine, structure, etc.), a reasonable estimation of the take‐off weight as well as the geometrical dimensions of a certifiable UAV are obtained.

Continuing wing production

Reviews the evolution of British Aerospace’s wing production facilities at Chester and Filton in the UK and on the design of the wings for the Airbus series of aircraft, from the first set of wings designed for the A300 in 1971 through to the A340‐500 and 600 and the A3XX. Reports on the design of the completely new wing for the A320 which was the first to incorporate fly‐by‐wire and other technologies. Discusses the design of load alleviation for defined manoeuvre and gust cases and the impact of a change in the airworthiness design case requirements on the design of the wing for the A321 and subsequent aircraft. Finally, the article examines the fully automated parts store at the British Aerospace Wing Centre at Filton.

Interactive Optimization-Based Design Software for Rotorcraft Flight Control Systems

A specialized software package, known as GIFCORCODE, has been developed to aid the designer of rotorcraft flight control systems. GIFCORCODE is based on CONSOL-OPTCAD (C-O), a software package that implements a design methodology based on multicriterion, parametric optimization. GIFCORCODE includes SIMULINK® and MATLAB® files for evaluating a design's performance, defined by the Airworthiness Design Standard for military rotorcraft (ADS-33C). GIFCORCODE also includes a generalized user interface that allows the designer to interact with C-O by means of pull-down menus and graphical displays. GIFCORCODE has been used in the design of flight control systems for the UH-60A RASCAL helicopter.

Improvement of helicopter handling qualities using H∞-optimisation

In the paper, we present the results of a study into the use of H∞-optimisation for the design of robust feedback control laws for improving the handling qualities of high-performance helicopters. A low-speed controller was designed to give accurate control of pitch and roll attitude, yaw rate and heave velocity for a typical combat helicopter. The design was based on a linearised model obtained from a six-degree-of-freedom nonlinear model of a helicopter provided by the Royal Aerospace Establishment (RAE), Bedford, UK. Robustness was a major issue because rotor dynamics were not included in the design model. Numerical compliance of the design with handling qualities requirements was assessed by testing simulated responses against specifications from a proposed airworthiness design standard. Robust stability was assessed from singular-value plots. In addition, the qualitative features of the design were assessed in a piloted flight simulation trial held at RAE, Bedford.

The Estimation of Tail Loading Due to Elevator‐Induced Pitching Manoeuvres

By application of the analytical method to a wide range of current aircraft types an approximate form of the method is developed for the quick estimation of tail load maxima and associated torques during the checked manoeuvre and the same is also confirmed for the unchecked manoeuvre of Ref. (3). Numerical values of critical elevator actions to be associated with the airworthiness design case are considered and hence, from a comparison with the approximate method, the limitations of the present empirical approach given in British and American civil airworthiness regulations are brought to light.